Observation and interpretation of spectra of atmospheric gravity wave perturbations with upward and downward phase progression
Observation and interpretation of spectra of atmospheric gravity wave perturbations with upward and downward phase progression
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DOI：
10.1029/94jd01118
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发表时间：
1994-08
影响因子：
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通讯作者：
S. Lintelman;C. Gardner
中科院分区：
文献类型：
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作者：
S. Lintelman;C. Gardner
我们提出了超过350小时的Na激光雷达测量的中间层（150 - 80公里）的密度扰动获得的50个夜晚，全年在伊利诺伊州厄巴纳。这些数据被用来研究扰动的频谱表现出向上和向下的相位进展。对于观测频率在ω0 = 2π/（120 min）和2π/（12 min）之间或垂直波数在m = 2π/（10 km）和2π/（1 km）之间的扰动，平均而言，三分之二的密度方差与呈现向下相位进展的扰动有关（即，向上传播的波），并且方差的三分之一与呈现向上相位进展的扰动相关联。夜间的变化高度相关，这表明向下和向上的相位扰动起源于相同的低空重力波源。理论模型结合多普勒效应的背景风推导出假设的内在频谱向上传播的重力波嵌入在一个均匀的水平流。这些模型被用来预测与向上和向下相位扰动相关的m和ω0谱指数和震级。对于ω0谱，测量的向上相位谱指数（平均值= −1.6）始终比向下相位谱指数（平均值= −1.9）浅。这一特性与Gardner [1994]的尺度无关扩散滤波理论的预测一致，但与Gardner等人[1993 a]的可分离重力波模型不一致，后者预测与向上和向下相位ω0谱相关的谱指数都近似等于本征谱的谱指数。两个模型都预测，对于30和50 m/s之间的水平风速，向上相位方差将接近总方差的20%至30%。这些是厄巴纳上空中层上层平均水平风的典型值。数据和模型预测强烈表明，在厄巴纳中层顶区域观测到的大部分波能与低层大气源产生的向上传播的重力波有关。
We present over 350 hours of Na lidar measurements of mesospheric (∼80–150 km) density perturbations obtained on 50 nights throughout the year at Urbana, Illinois. The data are used to study the spectra of perturbations exhibiting upward and downward phase progression. For perturbations with observed frequencies between ω0 = 2π/(120 min) and 2π/(12 min) or vertical wave numbers between m = 2π/(10 km) and 2π/(1 km), on average, two thirds of the density variance was associated with perturbations exhibiting downward phase progression (i.e., upwardly propagating waves) and one third of the variance was associated with perturbations exhibiting upward phase progression. The nightly variances were highly correlated which suggests that the downward and upward phase perturbations originate from the same low-altitude gravity wave sources. Theoretical models incorporating Doppler effects of the background winds were derived by assuming an intrinsic spectrum of upwardly propagating gravity waves embedded in a uniform horizontal flow. These models were used to predict the m and ω0 spectral indices and magnitudes associated with upward and downward phase perturbations. For the ω0 spectra the measured upward phase spectral indices (mean = −1.6) were consistently shallower than the downward phase spectral indices (mean = −1.9). This characteristic is compatible with the predictions of the scale independent diffusive filtering theory of Gardner [1994] but not with the separable gravity wave model of Gardner et al. [1993a] which predicts the spectral indices associated with the upward and downward phase ω0 spectra will both be approximately equal to the spectral index of the intrinsic spectrum. Both models predict that the upward phase variances will approach 20 to 30% of the total variance for horizontal wind velocities between 30 and 50 m/s. These are typical values for the mean horizontal winds in the upper mesosphere above Urbana. The data and model predictions strongly suggest that the majority of the wave energy observed in the mesopause region at Urbana is associated with upwardly propagating gravity waves generated by sources in the lower atmosphere.